The present invention relates to postage meters and more particularly to an electronic postage metering system including zip code-to-zone conversion.
The type of postal scale which is in widespread commercial use at present is a mechanical or electro-mechanical device for deriving postage as a function of package weight and destination zone.
While the Postal Service still uses zones for purposes of calculating postage on packages mailed from one part of the country to another, most people are not aware of which zone a particular destination falls in. They are, however, generally aware of the zip code at the destination. To permit a user to make a conversion from destination zip code to destination zone, the Postal Services publishes charts showing destination zones relative to a specific city of origin as a function of the first three digits or prefix of destination zip codes. The Postal Service also publishes another chart tabulating postage as a function of different weight-zone combinations. A user consults one chart to determine the proper zone and then, after weighing the package to be mailed, consults the other chart to find the proper postage. The user employs the retrieved postage entry to manually set a conventional postage meter to imprint the postage on a tape which can be affixed to the package.
U.S. Pat. No. 3,636,297, Salava, discloses a computer-type postage calculator in which the prefix of a destination zip code is converted to zone information through the use of a look-up table in which zones are stored as a function of zip code prefixes. The table is scanned in numerically ascending order until a correspondence is found between a user-entered destination zip code prefix and one of the addresses in the table. Signals representing the parcel weight, destination zone and class of handling are apparently algebraically added. The results would not appear to be consistently accurate. The calculator apparently would establish the same postage for a two-pound package being sent to zone 4 at parcel post rates as it would for a four-pound package being sent to zone 2 at the same rates. However, the Postal Service has established different postages for these two conditions. Moreover, the required memory or data storage capacity for such a system would be large and costly.